Subterranean chemical process



Nov. 10, 1964 J. c. TRANTHAM SUBTERRANEAN CHEMICAL PRocEss Filed Jan. 7, 1965 MVATIIII INVENTOR J. C. TRANTHAM A TTORNEVS United States Patent O 3,156,299 SUBTEAN CHEMICAL PROCESS `loseph C. Trantham, Bartlesville, Okla., assigner to Phiilips Petroleum Company, a corporation of Delaware Filed Jan. 7, 1963, Ser. No. 249,686 18 Claims. (Cl. 166-11) This invention relates to a process for in situ halogenation of hydrocarbons in a hydrocarbon-bearing subterranean stratum.

This is a continuation-in-part of my application S.N. 59,499, tiled September 30, 1960.

During recent years the recovery of oil by in situ combustion using both inverse and direct drive of a combustion front has taken on ascending importance. The process is effected by injecting oxygen-containing gas, such as air, into an ignited section of the stratum so as to burn a portion of the in-place hydrocarbon which supplies the heat for volatilizing and driving out remaining hydrocarbon material. Direct drive of the combustion front is effected by injecting air to the combustion front thru an input well, driving the front toward a production well, and recovering the produced hydrocarbons from the production Well. In the inverse process, the stratum is ignited around a production Well and air, preferably containing from 1 to 3 percent fuel gas, is injected thru an input well so that the air passes to the combustion front and produces hydrocarbons thru the production Well While moving the front countercurrently to the iiow of air toward the input well.

I have found that halogens and halogen-containing compounds react in situ with in-place hydrocarbon material so as to produce halogenated hydrocarbons.

Accordingly, it is a principal object of the invention to provide a process for producing halogenated hydrocarbons in situ from a hydrocarbon-bearing stratum. Another object is to produce both hydrocarbon and halogenated hydrocarbons in situ from such a stratum. A further object is to eiect halogenolysis of hydrocarbons in situ in a hydrocarbon-bearing stratum. Other objects of the invention will become apparent upon con sideration of the accompanying disclosure.

A broad aspect of the process comprises injecting a halogen-containing gas selected from the group consisting of Cl, Br, F, and interhalogen compounds thru a section of permeable hydrocarbon-bearing stratum so as to for-m halogenated hydrocarbons, and recovering the halogenated hydrocarbons from the stratum. The process may be carried out by direct drive injection where thecrude is not excessively viscous, and by inverse injection in other types of reservoirs or strata, particularly, those partially depleted by recovery methods. In the former case, the produced compounds tend to exert a solvent extraction effect, aiding in the movement of crude oil to the production well. In the latter case, the product is of lower lmolecular Weight resulting from halogenolysis and similar reactions which effect a splitting of the hydrocarbon molecules, together with substitution and addition reactions wherein the halogen is introduced to the low molecular weight hydrocarbon.

In addition to the halogens Cl, Br, and F, interhalogen compounds containing these halogens such as ClF3, BrF3, and BrF5, etc., are reactive with hydrocarbons to form chlorinated, fluorinated, and brominated hydrocarbons. The last two compounds are normally liquid but are readily vaporizable so that they may be injected in gaseous form, alone, or in admixture with a gaseous inert diluent such as nitrogen or CO2. The reactant gas may include more than one of the reactants, e.g., Cl, and BrF3 may both be injected simultaneously or in admixture. Since ICC the interhalo'g'en compounds are more reactive, their dilution with other gases helps to control the reaction. y

One embodiment of the invention comprises injecting the reactant gas at atmospheric or slightly elevated temperature into the stratum containing the hydrocarbon material. By slowly passing the halogen-containing gas thru a section of the stratum at stratum temperature, the temperature of the contacted stratum rises because of the exothermic nature of the halogenation and halogenated hydrocarbons of higher molecular Weight are produced. To illustrate this aspect of the invention, substantially pure chlorine gas was injected thru a tube packed with tar sand at room temperature. sand gradually rose to above F. and chlorinated hydrocarbons were produced.

It is preferred to heat the section of stratum to be contacted with the halogen, prior to injecting the halogen, so that the halogenated hydrocarbons produced are gaseous and readily recoverable. The lower molecular weight halogenated hydrocarbons are more valuable than the higher molecular Weight members. This aspect of the invention comprises igniting a section of stratum around an ignition borehole and feeding air or other oxygen-containing combustion-supporting gas to the hot stratum so as to effect in situ combustion and heat a substantial section of stratum. The air can be injected indirectly (inversely) to the heated area. If injected inversely, it s desirable to incorporate in the air a small concentration of fuel gas such as 1 to 3 volume percent of natural gas, propane, etc. The flow of air to the combustion front is then terminated and the halogencontaining gas is passed to the hot area of the stratum containing hydrocarbon material so as to eXothermically react the halogen and hydrocarbon, thereby maintaining an elevated reaction temperature Which effects halogenolysis. Temperature of reaction should be at least 600 and up to 1000 F. to obtain valuable products in good yield. A temperature in the range of 700 to 900 F. is preferred.

It is also feasible to incorporate air or other O2-con taining gas, such as pure oxygen, diluted air, or air enriched with oxygen, with the halogen-containing gas so that both oxidation and halogenolysis are simultaneously effected. The concentration of halogen in this embodiment of the invention should be at least 25 volume percent of the injected gas. This technique contributes to higher halogenation temperatures and better products.

Another aspect of the invention comprises alternately injecting the oxygen and the halogen so as to effect a cycle of operation in which hydrocarbons and halogenated hydrocarbons are alternately produced. This feature of the process assures high temperature halogenation and .lower molecular weight, more valuable product.

One method comprises establishing a combustion Zone around an ignition well which is to serve either as a production well (inverse injection of gas) or an injection Well (direct injection of gas). While the ignited section of stratum is hot, halogen is injected either thru the ignition well or thru a ring of olset injection Wells so that the injected halogen passes to the hot section of stratum and rapidly reacts with the hydrocarbon material therein. In the case of inverse injection of the halogen, some reaction of the halogen takes place as it passes thru the stratum prior to reaching the hot zone; but the halogenated hydrocarbon produced in advance of the high temperature front is eventually produced thru the production Well. By injecting the halogen thru the ignition well, the produced gases including halogenated hydrocarbons serve as a ushing and solvent fluid for producing hydrocarbons from the stratum.

The stratum may be heated by other means than by in situ combustion, such as by means of a downhole heater The temperature of theor by injection of hot inert gas thru the section of stratum to be heated. It is also feasible to inject the halogen into a production well which is packed oif around a tubing at an intermediate level in the stratum so that the injected halogen passes thru an annular section of stratum along the borehole. The borehole can be packed olf just below the top and just above the bottom of the stratum by means of packers around the well tubing and the halogencontaining gas can be injected either thru the casing-tubing annulus or thru the tubing, with recovery of the produced gases thru the alternate path not used by the injected gas. In other words, by injecting thru the tubing the halogen passes thru the stratum around the packers and the produced gases enter the Well bore above the upper packer from which they are recovered thru the casing-tubing annulus. As in other aspects of the process, the section of stratum around the well bore may be heated prior to the injection of halogen.

The process is applicable to virgin strata or to partially depleted strata. When preheating the stratum before a halogen injecting step it is preferred to heat to a temperature of at least 200 F. and preferably at least 400 F.

To further illustrate the invention, a 38 mm. Vycor tube about 12 inches long was packed with Bellamy tar sand. It Was preheated to 300 F. with an electrical heating tape and counterflow combustion Was started on air by heating the outside of the tube with a torch. As soon as combustion was underway the air was replaced with a stream of chlorine and the hydrocarbon material in the sand burned in a chlorine atmosphere for a short distance but died out when the small amount of t-ar sand available in the tube was spent. A small amount of a dense oil, evidently a chlorinated hydrocarbon (heavier than water) was recovered. Distillation gave a Water-white, dense liquid containing 53 wt. percent Cl and having a molecular weight of 130. There was insufficient material for other tests, but Within `the analytical error on a sample this small, the molecular Weight and chlorine content correspond to the dichlorobutanes. This indicated that chlorinolysis of the tar had taken place during counterflow combustion in chlorine.

When operating at high temperatures such as 600 to 1000o F., low molecular weight halogenated hydrocarbons are produced. These range from monohalomethane to dihalobutanes and higher molecular Weight hydrocarbons. Also, significant amounts of haloacids such as HC1 are formed.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing of which FIGURE l is an elevation in partial section thru a well in a carbonaceous stratum illustrating one ernbodiment of the invention; and FIGURE 2 is a similar view illustrating a second embodiment of the invention.

Referring to FIGURE l, a stratum is penetrated by a well l2 which is provided with a casing 14 and a tubing 16. Line IS connects with the Well annulus thru casing 14. Stratum 10 is fractured in conventional manner at -two vertically spaced levels to produce fractures and 22. The fractures are propped in the usual manner and the intermediate annulus is packed oif by means of packer 24.

Producing with the arrangement shown in FIGURE 1 involves heating a section of the stratum adjacent either fracture 20 or fracture 22 to suitable reaction temperature for hydrocarbons in the stratum to react with halogen, and a fluid providing halogen is injected either thru tubing 16 or thru line 18 and annulus 26. Assuming that the stratum adjacent fracture 20 is heated -to a reaction temperature, as by injecting hot gas into the fracture and producing thru fracture 22 and tubing 16, the halogenproviding gas is then injected either thru the annulus directly into the hot stratum adjacent fracture 20 with production thru fracture 22 and tubing le, or the halogen is injected thru tubing I6 into the fracture 22 so that it passes vertically thru stratum 10 into the hot section adjacent fracture Z0, thereby effecting the desired halogenation and producing the halogenated hydrocarbons thru annulus 26 and line I8. In the event the halogen-containing i'luid is injected directly into fracture 20 and the hot adjacent section, the reaction zone is moved toward fracture 22 as in a direct drive combustion process. In this type of drive, the halogenated hydrocarbons are driven thru the unproduced stratum and, because of their solvent action, aid in the movement of crude oil to the production Well. The movement of the hot reaction zone thru the stratum as Well as lthe movement of the hot products therethru produces unhalogenated hydrocarbons as Well as halogenated hydrocarbons thru the production Well. The direct drive of the reaction or combustion zone is generally preferably practiced on reservoirs in which the crude is not excessively viscous. Inverse movement of the reaction or combustion Zone thru the stratum is practiced in reservoirs containing either light or heavy crude. In the latter type of drive, usually termed inverse drive, the products are of lower molecular Weight resulting from halogenolysis and similar reactions.

Of course, it is feasible to heat the stratum adjacent fracture 22 and inject the halogenating feed either thru tubing 16 or thru line i8 and annulus 26 into fracture 20 from which it flows thru the stratum to the hot reaction zone along fracture 22.

Production of halogenated hydrocarbons can be effected around an unfractured Well by injecting the reactant halogen into the stratum at one level and producing the halogenated hydrocarbons at another level therein by blocking off or packing off the intervening annulus so that the ilow of fluid is thru the stratum around the packer or packed off section of annulus.

In FIGURE 2 stratum 10 is penetrated by Wells 30 and 32 one of which may represent either a central well in a 5-, 7-, or 9-spot pattern While the other well represents one of the Wells in the ring; or each Well may represent a Well in `two parallel lines of wells arranged for a line drive production process. Well 30 is provided with casing 34 and tubing 36; and well 32 is provided with casing 38 and tubing 40. Heater 42 is positioned on tubing 36 for heating stratum 10 around well 30. Lines 44 and 46 connect with casing 34 and 38, respectively, for injection or withdrawal of fluids from the Wells.

In operation, the stratum around well 30 is heated up to an elevated reaction temperature with halogen by means of heater 42 which may be an electric heater or a gas-fired heater. In the event 42 is a gas-fired heater, the combustion gas and any vaporized hydrocarbons produced in the heating are produced thru line 44. It is also feasible to produce the combustion gas thru Well 32 in a stratum which is not subject to plugging by forcing hot liquid hydrocarbons into the cold stratum Where they Congeal. In a stratum containing less viscous hydrocarbon material, this procedure is applicable and is also feasible to heat this type of stratum by injecting hot gas thru the well head and thru tubing 36 into the stratum to force the same thru the stratum into Well 32.

When the stratum has been heated to suiiiciently high temperature to sustain the halogenation process, the heating step is discontinued and the halogen-containing fluid is injected either thru well 30 or Well 32. In the event the stratum lli) is not amenable to direct drive because of the viscous nature of the hydrocarbons therein, the halogen is supplied thru well 32 (either thru conduit 46 or tubing 40) so that the halogen feed passes thru the stratum to the hot section thereof around well 30 and effects the halogenation reaction. The reaction zone moves thru the stratum countercurrently to the flow of halogen, the halogenated product and unhalogenated hydrocarbon material being produced thru well 30 in conventional manner for producing hydrocarbons.

In strata containing less viscous hydrocarbon material, the halogen may be injected thru well 30 so as to drive the reaction Zone thru the stratum to well 32. In this direct drive process, well 32 is a production well while well 30 is an injection well.

In order to illustrate and demonstrate the invention, a test was carried out in the laboratory utilizing Danglemayer crude oil on crushed Barnsdall sandstone packed in a 11/2-incl1 diameter Vycor tube. One end of the packed sand was heated to 500 F. by means of an electric heater, and chlorine gas was then injected into the opposite end of the packed sand so that it travelled thru the sand to the hot section at the end opposite the injection end. The gaseous and liquid products produced in the reaction were collected and separately analyzed. The liquid product was analyzed by infrared analysis which showed that the chlorinated hydrocarbons were mostly paratlinic with a small aromatic portion. Six samples of the efliuent gas were collected and chromatographically analyzed. The chromatographic analyses are presented in the table below.

The character of the halogenated hydrocarbon can be controlled to some extent by controlling the temperature of reaction and the type of movement of the reaction zone, i.e., direct drive or countercurrent drive of the combustion zone. Lighter halogenated hydrocarbons are produced in the inverse drive process and at higher reaction temperatures. The reaction temperature may be controlled to some extent by the initial heating and by injecting a minor but substantial concentration of free O2 in the injected halogen-containing feed, also, by alternate injection of halogen and air or iner-t gas such as CO2, combustion gas, nitrogen, etc.

Certain modications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A process for producing halogenated hydrocarbons in situ in a subterranean stratum containing hydrocarbons and recovering the halogenated hydrocarbons which comprises injecting at least one reactive halogen selected from the group consisting of Cl, Br, and F and interhalogen compounds thereof into a section of said stratum thru a well therein and contacting said hydrocarbons with said halogen in gaseous form under halogenating conditions so as to halogenate hydrocarbons as the principal reaction therein; continuing the injection of said halogen so as to drive resulting halogenated hydrocarbons into a well in said stratum; and producing an effluent from last said well containing said halogenated hydrocarbons.

2. The process of claim 1 wherein said section is heated to an elevated temperature prior to the injection of said reactant.

3. The process of claim 2 wherein O2-containing gas 6 is injected into said section and the same is heated by burning in-place hydrocarbons with said injected O2.

4. The process of claim 1 wherein said reactant comprises Cl.

5. The process of claim 1 wherein said reactant comprises Br.

6. The process of claim 1 wherein said reactant comprises F.

7. The process of claim 1 wherein said reactant comprises ClF3.

8j. The process of claim 1 wherein said reactant comprises BrF3.

9. The process of claim 1 wherein said reactant comprises BrF5.

10. A process comprising heating a section of a hydrocarbon-bearing stratum around an ignition well to at least 600 F. by igniting the same and burning hydrocarbons therein with O2 injected through said well; passing thru the resulting hot section from a well in said stratum a gaseous reactant containing at least 25 volume percent of at least one member of the group consisting of Cl, Br, F, and interhalogen compounds thereof so as to form principally C1 to C4 halogenated hydrocarbons; and recovering the effluent product, including halogenated hydrocarbons, from a well in said stratum.

11. The process of claim 10 wherein said reactant is injected thru said ignition well, and the reaction product, including said halogenated hydrocarbons, is recovered thru at least one offset production well.

12. The process of claim 10 including alternately injecting O2 and said gaseous reactant thru said ignition well so as to effect alternate periods of burning with the resulting production of hydrocarbons and halogenolysis with the resulting production of light halogenated hydro carbons.

13. The process of claim 10 wherein O2 is included in said gaseous reactant so as to simultaneously produce hydrocarbons by oxidation and halogenated hydrocarbons by halogenolysis.

14. The process of claim 10 wherein said reactant comprises Cl.

15. The process of claim 10 wherein said reactant is injected thru at least one offset well closely spaced from said ignition Well so as to pass the same to said section and react with hydrocarbons therein; and recovering said product thru said ignition well.

16. The process of claim 10 wherein said stratum is fractured at vertically spaced levels around said ignition well; said stratum is heated along one fracture; said halogen is injected thru one fracture; and products are produced thru the other fracture level.

17. The process of claim 16 wherein said halogen is injected into the fracture thru which the stratum is heated.

18. The process of claim 16 wherein said halogen is injected into the fracture remote from the heated stratum, thereby passing thru the stratum to the heated section.

References Cited in the le of this patent UNITED STATES PATENTS 1,999,146 Ambrose et al. Apr. 23, 1935 2,804,146 Crawford Aug. 27, 1957 2,857,002 Pevere et al. Oct. 21, 1958 3,051,235 Banks Aug. 28, 1962 

1. A PROCESS FOR PRODUCING HALOGENATED HYDROCARBONS IN SITU IN A SUBTERRANEAN STRATUM CONTAINING HYDROCARBONS AND RECOVERING THE HALOGENATED HYDROCARBONS WHICH COMPRISES INJECTING AT LEAST ONE REACTIVE HALOGEN SELECTED FROM THE GROUP CONSISTING OF CL, BR, AND F AND INTERHALOGEN COMPOUNDS THEREOF INTO A SECTION OF SAID STRATUM THRU A WELL THEREIN AND CONTACTING SAID HYDROCARBONS WITH SAID HALOGEN IN GASEOUS FORM UNDER HALOGENATING CONDITIONS SO AS TO HALOGENATE HYDROCARBONS AS THE PRINCIPAL REACTION THEREIN; CONTINUING THE INJECTION OF SAID HALOGEN SO AS TO DRIVE RESULTING HALOGENATED HYDROCARBONS INTO A WELL IN SAID STRATUM; AND PRODUCING AN EFFLUENT FROM LAST SAID WELL CONTAINING SAID HALOGENATED HYDROCARBONS. 